In recent years, with the spread of radio terminals such as smartphones that can execute a large number of applications, the frequency at which radio terminals are connected to a network and the frequency at which a network performs paging of radio terminals have been increasing.
For this reason, in the mobile communication system, a network load associated with signaling is increasing. Under such circumstances, in 3rd generation partnership project (3GPP) which is a standardization project of a mobile communication system, technology for reducing signaling is under review.